1. Field of the Invention
The present invention relates to a vehicle lamp, having a lamp body formed by resin molding, and more particularly to a vehicle lamp in which the lamp body is prevented from deforming after the molding process.
2. Description of the Related Art
Resin molding can be used to form a lamp body of a vehicle lamp such as an automobile. For example, for a front turn signal lamp disposed in an opening provided in a front bumper of an automobile, a lamp body 1 with a flat, rectangular front view and a paraboloidal rear surface portion as shown in FIG. 4, is formed by resin molding. The inner surface of the body 1 is coated with aluminum to form a reflecting surface. In addition, a seal groove 14 is formed in a front opening 1a of the lamp body 1 along its peripheral edges, and a lens 2 is attached to the front opening 1a of the lamp body 1 by making use of the seal groove 14. Further, a bulb 4 is detachably mounted in a bulb mounting sleeve 15 provided on a rear surface portion 11 of the lamp body 1 by using a bulb socket 5. Since the arrangement of this lamp is such that the lamp body 1 is formed to have a flat, rectangular front view as described above, peripheral side surface portions including upper and lower surface portions 12 and left and right surface portions 13 of the lamp body 1 are formed with flat shapes that extend in the forward direction substantially vertically and in parallel from the rear surface portion 11, which has the shape of a paraboloid.
FIG. 6 is a vertical cross-sectional view of the conventional lamp of the foregoing type. It can be seen from the drawing that the upper and lower surface portions 12 of the lamp 1 are formed to be flat surfaces extending in the forward direction in parallel from the rear surface portion 11 having the shape of a paraboloid.
In the above-described lamp body 1, to satisfy the required mechanical strength, the thickness of the resin from the rear surface portion 11 to the upper and lower surface portions 12 and the left and right surface portions 13 is designed to be of a sufficient and uniform thickness. Resin molding of the lamp body 1 is carried out by using a resin mold that fabricates the designed thickness.
In the above-described conventional lamp body 1, the thickness of the resin from the rear surface portion 11 to the peripheral side surface portions 12 and 13 is designed to be uniform. However, since the rear surface portion 11 and the peripheral side surface portions 12 and 13 meet each other close to an orthogonal angle, the diagonal thickness t12 of a portion whose diagonal thickness between the two portions is made large. That is, the portion indicated by X in the enlarged view of FIG. 6, becomes larger than the thickness t11 of the other uniform portions. For this reason, when the molded lamp body 1 is cooled after resin molding using the mold, the cooling of the X portion with the large thickness is retarded compared to other portions. Because of the difference in the cooling rate, an internal stress occurs in the lamp body 1. This internal stress appears in the form of deformation at portions of the lamp body 1 where the mechanical strength is relatively weak. In the lamp body, such as shown in FIG. 4, which has a flat shape and has an extensive depth as described above, the upper and lower surface portions 12 have larger areas compared to the left and right surface portions 13. The strength of the portions 12 against bending is, therefore, relatively low. Hence, as shown by two-dotted dash lines in the drawing, the upper and lower surface portions 12 are deformed in the state of being inwardly curved. When such deformation occurs, the lens may be prevented from being mounted in the front opening 1a of the lamp body 1. In noticeable cases, the lamp may not be used as a product, so that its production yield declines. In addition, even if the lens 2 can be attached and the parts can be assembled as a lamp, it is difficult to completely eliminate the deformation of the upper and lower surface portions of the completed lamp. Therefore, the external appearance is impaired, which constitutes as a factor that deteriorates the quality of the lamp.
An object of the invention is to provide a vehicle lamp configured to prevent deformation of its lamp body after resin molding and to permit formation of the lamp body of high quality.
The vehicle lamp includes a lamp body, which has a rear surface portion with a required surface shape and peripheral side surface portions formed to extend in a forward direction from a periphery of the rear surface portion. The rear surface portion and the peripheral side surface portions are integrally formed by resin molding, and a lens is provided in a front opening of the lamp body. Thin-walled portions are provided in which the thickness of the peripheral side surface portions or both the peripheral side surface portions and the rear surface portion along boundary portions where the rear surface portion and the peripheral side surface portions meet is made smaller than that of other portions. In particular, in an embodiment of the lamp body having a flat shape from a front view and a shape with extensive depth, each of the thin-walled portions is preferably formed at the boundary portion between the rear surface portion and each of upper and lower surface portions forming the peripheral side surface portions.
In embodiments of the invention, the thin-walled portions are provided, in which the thickness of the peripheral side surface portions or both the peripheral side surface portions and the rear surface portion is decreased along the boundary portions where the rear surface portion and the peripheral side surface portions meet. Because of the thin-walled portion, when the resin is being cooled after resin molding, the cooling rate of the boundary portions can be prevented from being slower than the cooling rate of the other portions, and the generation of stress in the lamp body can be suppressed.
In particular, since regions in the peripheral side surface portions are made thin in the boundary portions to form the thin-walled portions, the generation of stress at the peripheral side surface portions can be suppressed to prevent their deformation. In addition, for a large lamp body having substantial width and depth, the deformation of the upper and lower surface portions with large areas can be prevented by forming the thin-walled portions at the boundary portions between the rear surface portion and the upper and lower surface portions.